@Summ: SHIFT might be more colourful, but I find GT5 much more realistic when it comes to colours. I don't find it sterile at all, I find it very realistic. I'm amazed each time I see GT5 Prologue or Forza 3 in action. As for the car models, I think you should check the cars in SHIFT more carefully. I could show you right now some pictures of the game where you clearly see that the models don't have much polygons. As an example, I was checking yesterday my beautiful RX-7 for drift, and I noticed that the headlights textures are low resolution and the overall look of the car (mainly the front bumper) has a low amount of polygons, so instead of seeing a nice and smooth curve, you see some straight lines that work as a curve. You don't see that in Forza 3 or GT5, believe me. The decals, for example, are also very "pixelized". And that's not the only thing, some textures in the track also lack detail.
The only way to "officially" confirm this is of course having a car from SHIFT and another from GT5 in 3D view and count the amount of polygons. You'll see how much more polygons GT5 has compared to SHIFT. Just looking at them carefully is enough to see this, but having both models in 3D would be a definitive proof.
Of course that this doesn't mean SHIFT has bad models. It's the best NFS so far when it comes to graphics, and I really like the look of the game. But they're worse than the ones in GT5 and Forza 3, which seem to be the main "opponents" of SHIFT. Just that.
As for the trackside 3D objects, they wouldn't hurt the framerate that much if they would optimize the game engine. I know plenty of games who deal with a massive amount of information and they run perfectly fine when the producers work hard. Of course that this is a design decision, not to have much "outside of the track objects". But after playing GRID, I can't help myself but think that more companies should improve the surroundings in their tracks. Forza 3, for example, seems to lack this too. Everything that is outside the circuit itself is not very detailed, things look empty, dead.
This is not the most important for a racing game, true. The design of the cars and the tracks are far more important than the surroundings. However, I find them important too if you want to have an even more realistic environment. I felt like being on a race car while playing GRID. The reactions of the crowd, the sounds of the crowd, the barriers and walls getting deformed when you crash on them, the surroundings with trees, buildings and so on.
As for GRID, the game is from 2008 and SHIFT is from 2009, so don't compare them. If you want, compare SHIFT to DiRT 2, and you'll see that DiRT 2 (even being a rally game) offers much more detail than SHIFT. GRID is older, so it's normal that its graphics don't look as good as when it was released. The bloom effects you point out are in fact one of the things I don't like in the game, but I think there's a mod for the PC version that remove them, and it looks much better. Still, if you look "outside" the track, you see plenty of little things they inserted to make it more realistic and enterteining. Of course that they don't have so much detail as the cars or the circuit, but they look good IMO. And GRID is very unique when it comes to that. Most racing games just don't care about the surroundings, while GRID focus on that much more. I feel that's the way to go. After we get ultra realism inside the track, it's time to take that realism outside the track and make things much better. This is my opinion of course, but I really think that this is what we will get in the future.